Nimbostratus Clouds

dark, low-level clouds with precipitation

Nimbus means rain, and stratus means sheet, so nimbostratus is a sheet cloud from which rain or snow is falling, usually continuously. Nimbostratus forms when warm, moist air is lifted steadily over a large area.

Nimbostratus are dark, low-level clouds accompanied by light to moderately falling precipitation.The layer is thick enough to block out the sun.

Low clouds are primarily composed of water droplets since their bases generally lie below 6,500 feet (2,000 meters). However, when temperatures are cold enough, these clouds may also contain ice particles and snow.